1. Field of the Invention
The present invention relates generally to short-range wireless communication, and more particularly, to a communication method and apparatus for the coexistence of a plurality of piconets in a Wireless Body Area Network (WBAN) environment.
2. Description of the Related Art
WBAN refers to specific short-range wireless communication which is progressing towards the international standard IEEE (Institute of Electrical and Electronic Engineers) 802.15.6 TG6 BAN. WBAN can be used in medical services, such as remote health care, and entertainment services for wearable computing or using motion sensors, through a communication network in a body area within about three meters.
In WBAN, each individual constitutes one network, referred to as a “piconet”. The piconet may be comprised of one coordinator node and a plurality of device nodes. The coordinator node may be a mobile phone and the device nodes may be a variety of personal devices attached to a human body. WBAN acts similar to a sensor network, and thus is prone to the “collision problem” caused by interference between a plurality of piconets when many people are present in a restricted space or while people move. Accordingly, a design of a specialized Medium Access Control (MAC) protocol for WBAN is demanded.
To design the specialized MAC protocol for WBAN, Carrier Sense Multiple Access (CSMA) and Time Division Multiple Access (TDMA) may be considered.
CSMA does not require time synchronization between nodes and shows a high channel utilization ratio and a low delay in a low contention environment. However, in a high contention environment (in which the number of nodes within an interference range is increased), performance deterioration occurs due to an increase in collisions and an increase in unpredictable delay caused by backoff. Therefore, it is difficult to apply CSMA to a WBAN when a plurality of piconets are present in a narrow space, and a real-time response is required.
TDMA has the advantages of a high channel utilization ratio, fewer collisions, and no unpredictable delay in a high contention environment but has the problem of overhead caused by time synchronization. Generally, TDMA requires a reference node for time synchronization, that is, a time synchronization root and consumes much time and energy for time synchronization when a node enters a new node or moves.
Accordingly, studies are needed in WBAN on a MAC protocol in a convergence form of CSMA and TDMA, which can overcome the disadvantages of the two schemes.